[PATCH for-4.5] x86/hvm: do not create ioreq server if guest domain is dying

[Vitaly Kuznetsov <vkuznets@redhat.com>]

If HVM_PARAM_IOREQ_PFN, HVM_PARAM_BUFIOREQ_PFN, or HVM_PARAM_BUFIOREQ_EVTCHN
parameters are read when guest domain is dying it leads to the following
ASSERT:

(XEN) Assertion '_raw_spin_is_locked(lock)' failed at ...workspace/KERNEL/xen/xen/include/asm/spinlock.h:18
(XEN) ----[ Xen-4.5-unstable  x86_64  debug=y  Not tainted ]----
...
(XEN) Xen call trace:
(XEN)    [<ffff82d08012b07f>] _spin_unlock+0x27/0x30
(XEN)    [<ffff82d0801b6103>] hvm_create_ioreq_server+0x3df/0x49a
(XEN)    [<ffff82d0801bcceb>] do_hvm_op+0x12bf/0x27a0
(XEN)    [<ffff82d08022b9bb>] syscall_enter+0xeb/0x145

It doesn't make sense (and is unsafe) to create ioreq server if we're dying. Make
hvm_create_ioreq_server() fail with -EFAULT in this case.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 xen/arch/x86/hvm/hvm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 0a20cbe..2cc6de7 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1038,6 +1038,9 @@ static int hvm_create_ioreq_server(struct domain *d, domid_t domid,
     struct hvm_ioreq_server *s;
     int rc;
 
+    if ( d->is_dying )
+        return -EFAULT;
+
     rc = -ENOMEM;
     s = xzalloc(struct hvm_ioreq_server);
     if ( !s )
-- 
1.9.3